1. Field of the Invention
The present invention concerns flywheels for transmission systems, of the kind usually constituting an inertial member in clutches, especially clutches designed to be fitted to automobile vehicles.
It is more particularly directed to flywheels, known as damper-type flywheels, incorporating damper means operative against possible torsional torques.
2. Description of the Prior Art
It is usual to incorporate a torsional damper device in a transmission system to filter out vibration that can arise anywhere in the kinematic system that the transmission constitutes, extending from the motor to the wheel axles in the case of an automobile vehicle.
The torsional damper device is usually incorporated in the friction disk of the clutch.
However, it has also been proposed to incorporate a torsional damper device in the flywheel, either instead of or in conjunction with the damper device in the friction disk, for certain applications of a specific kind, in particular for vehicles where the motor develops a relatively high torque at low rotation speeds, where there may be a particular requirement to eliminate "trash" noise which occurs under load.
This is the case, for example, with the damper-type flywheel that is the subject matter of German patent No. 29 31 423.
Generally speaking, a damper-type flywheel of this kind comprises two coaxial parts disposed to rotate relative to each other, namely a first part comprising two spaced annular flanges and a second part comprising an annular flange assembly adapted to lie between the annular flanges on the first part, and circumferentially acting spring means and friction means operative between the first and second parts, the circumferentially acting spring means in practise comprising circumferentially acting spring members accommodated in respective openings provided for them in the annular flanges, arms forming part of the flange assembly being adapted to interfere with these spring members, with circumferential clearance between the spring members and the arms.
In the proposed embodiments the friction means are in practise of two types.
Firstly there are friction means which are operative from the beginning of and throughout relative angular displacement between the two coaxial parts concerned and which are the only means operative between the coaxial parts during a first part of their relative angular displacement, the spring members provided between these coaxial parts only becoming operative during a second portion of this movement.
Secondly there are friction means associated with a much higher torque than the relatively moderate torque associated with the previously described friction means and which, being operative in practise in series with the other component parts of the damper-type flywheel, constitute a torque limiter the function of which is, by introducing slippage, to absorb any excess torque that may arise because of resonance between the two coaxial parts concerned on relative oscillation between them, especially on starting up and stopping.
A particular disadvantage of a torque limiter of this kind is that it has to correspond to a torque greater than the motor torque and may lead to malfunctions should it be damaged since, being operative in series with the other components, the torque to be transmitted has to pass through it.
A general objective of the present invention is an arrangement which is advantageously free of such disadvantages whilst providing for absorption of any excess torque.